MANIPULATION OF ARACHIDONIC ACID IN THE DIET OF ADULT CALIFORNIA YELLOWTAIL Seriola lalandi

Marine finfish require highly unsaturated fatty acids (HUFAs) for normal physiological function, and because these HUFAs cannot be synthesized by the fish they must be obtained from the diet.  Three HUFAs-arachidonic acid (ARA; c20:4 n-6), eicosapentaenoic acid (c20:5 n-3) and docosahexaenoic acid (c22:6 n-3) are especially important for growth and development of marine fish embryos and larvae.  Here we supplemented ARA in the diet for a serial spawner, California yellowtail (CYT; Seriola lalandi), to determine if ARA would impact egg and larval quality.

We used a Hobart mixer and mash premix (Bio Vita Starter Mash; Bio-Oregon) to formulate experimental diets in sausage form of 3.0 cm diameter cut to 8.0 cm in length.  Diet 1 was the commercial premix without ARA supplementation, Diet 2 was the commercial premix with 1.0% ARA added.  Each treatment diet was fed to two replicate tanks of four CYT (2 males, 2 females).  The CYT brood fish were 7 year old F1s averaging 8.9 kg each.  Feeding was initiated at the beginning of 2015, three months prior to the spawning season.  At that time, the fish were transitioned from sardines to the experimental diets at a ration of 3-5% body weight per day for five days of the week.  The fish were held in 10 m³ tanks under ambient water temperature and photoperiod conditions

Fish in the control treatments spawned 41 times for a total of 16.0 million eggs.  Of those events, 20% exhibited ≥70% viability.  Fish in the ARA treatment tanks spawned 20 times for a total of 11.1 million eggs.  Of those events, 50% exhibited ≥70% viability.  Egg quality measurements; egg diameter, oil diameter, percent oil volume, larval length at hatch, hatch rates, and survival to first feeding did not show any statistical differences between treatments.      We demonstrated that CYT will spawn successfully in small breeding tanks of 10 m³, which facilitates manipulative studies of broodstock nutrition as reported here.  Data thus far are preliminary, but represent an excellent starting point for dietary refinements in the future, helping to ensure the best possible egg quality.